TDOT Explains Why 'Zipper Merge' Not In TN

Posted at 6:46 PM, Feb 23, 2017

Every driver's been there. A lane is closed for a crash or construction and you have to merge into a single line of traffic, but do you get over ahead of time, or do drive to the closure, waiting until the last minute?

That's the difference between an early merge, when drivers get over as soon as they see a lane closure, and the technique a handful of states have tested.

"It's all about work zones and reducing speed and crashes in work zones," said Minnesota Dept. of Transportation spokesperson Kevin Gutknecht in a FaceTime interview with NewsChannel 5 Traffic Anchor Rebecca Schleicher Thursday.

It's called a zipper merge. Drivers fill both lanes until the lane ends, taking turns getting by the closure. Picture it like the parts of a zipper coming together, in turn.

"What you avoid then is having this big empty lane where people speed down to the merge point then stop and wait and try to get in," Gutknecht said.

In the more than five years since Minnesota started using the zipper merge, teaching it to drivers through a massive public awareness campaign, the state reported fewer crashes. Staff said it's cut down on traffic near work zones by up to 40 percent.

The concept has caught the Tennessee Dept. of Transportation's attention, but spokesperson BJ Doughty said Tennessee has heard mixed reviews from different states that have tried it.

"This technique depends a lot on the motorist doing what they're supposed to do," she said, "quite frankly we have a hard enough time getting people to read signs."

Staff also worried about road rage resulting from the confusion of a different way of doing things.

"I'm not hearing many (road rage) incidents," Gutknecht said, "though I supposed there are the periodic salutes people make to each other."

TDOT said, near Nashville, shutting down an entire road for short intervals like the Fast Fix 8 bridge project last year works better, at least for now.

"We have a lot of different ways to get around the city," Doughty said. So if a road is shut down, there are other interstates and loops like I-440 and Briley Pkwy people can use as an alternate route to their destination.

Zipper merging goes against what many people think is right, and are used to doing.

"From kindergarten on we're told we need to stand in line and stay in place in line," Gutknecht said. Sometimes truck drivers will even block the second lane, thinking they're helping but actually disrupting the zipper merge.

Yet, if success continues elsewhere, TDOT said it could consider the zipper merge in the future.